NSMetaDataQuery：没有收到更新或收集完成的通知

Question

我正在尝试一些代码来使用 NSMetaDataQuery 来获取基于应用程序路径 在捆绑标识符上。我正在关注在苹果开发中找到的 hte 示例代码 site：静态 Spotlight 搜索实现。

我为它写了以下文件

//AppPath.h

void GetAppPath();

@interface SearchQuery: NSObject 
{

}

@property (copy) NSMetaDataQuery *metaData;

-(void) initiateSearch;
-(void) queryDidUpdate:sender;
-(void) initalGatherComplete:sender;
@end

定义如下：

void GetAppPath()
{
    SearchQuery *query = [[SearchQuery alloc] init];
    [query initiateSearch];
}

@Implementation SearchQuery

// Initialize Search Method
- (void)initiateSearch
{
    // Create the metadata query instance. The metadataSearch @property is
    // declared as retain
    self.metadataSearch=[[[NSMetadataQuery alloc] init] autorelease];

    // Register the notifications for batch and completion updates
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(queryDidUpdate:)
                                                 name:NSMetadataQueryDidUpdateNotification
                                               object:self.metadataSearch];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(initalGatherComplete:)
                                                 name:NSMetadataQueryDidFinishGatheringNotification
                                               object:self.metadataSearch];

    // Configure the search predicate to find all application with the given 
    //Bundle Id
    NSPredicate *searchPredicate;
    searchPredicate=[NSPredicate predicateWithFormat:@"NSApplicationBundleIdentifier == 'com.myapp.app'"];
    [self.metadataSearch setPredicate:searchPredicate];

    // Begin the asynchronous query
    [self.metadataSearch startQuery];

}

// Method invoked when notifications of content batches have been received
- (void)queryDidUpdate:sender;
{
    NSLog(@"A data batch has been received");
}


// Method invoked when the initial query gathering is completed
- (void)initalGatherComplete:sender;
{
    // Stop the query, the single pass is completed.
    [self.metadataSearch stopQuery];

    // Process the content. 
    NSUInteger i=0;
    for (i=0; i < [self.metadataSearch resultCount]; i++) {
        //Do Something with the result
    }

    // Remove the notifications to clean up after ourselves.
    // Also release the metadataQuery.
    // When the Query is removed the query results are also lost.
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:NSMetadataQueryDidUpdateNotification
                                                  object:self.metadataSearch];
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:NSMetadataQueryDidFinishGatheringNotification
                                                  object:self.metadataSearch];
    self.metadataSearch=nil;
}

@end

我正在调用main 中的GetAppPAth 方法。我已经添加了必要的头文件。代码编译并运行，但我没有收到两个观察者的任何通知。 我在queryDidUpdate 和initalGatherComplete 这两种方法中设置了断点。但他们永远不会被击中。我认为失败是因为我的主要代码不是 等待搜索完成。但即使我在 main 中进行了一些等待，它也无法正常工作。我还尝试过以下问题中的代码：Not quite understanding NSMetadataQuery 但它以无限的while 循环结束。

Answer 1

从您发布的代码示例来看，SearchQuery 似乎没有被任何东西保留，因此它会立即被释放。